Pharmacology 3620 Lecture Notes - Lecture 7: Insulin, Mesna, Skeletal Muscle
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| receptor | Agonist | antagonist | |
| a1 | Norephinephrine | Phenylephrine | |
| a2 | Phenoxybenzamine | Prazosin | |
| B1 | Clonidine | Yohimbine | |
| Norephinephrine | Propranolol | ||
| Epinephrine | Metoprolol | ||
| Isoproterenol | |||
| Dobutamine | |||
| B2 | Epinephrine | Proranolol | |
| Norepinephrine | Butoxamine | ||
| Isoproterenol | |||
| Albuterol | |||
| Nicotinic | Ach | Curare | |
| Nicotine | |||
| Hexamethonium | |||
| Muscarinic | Ach | Atropine |
Assume all the chemicals in the table are available to you.
You are given a piece of smooth muscle tissue, you stimulate it with Norepinephrine and find the muscle responds with contractions. Your hypothesis is that the muscle contraction is caused by the activation of α1 adrenergic receptors. Now you need to design an experiment protocol to test your hypothesis.
Background knowledge: The figure below is an experiment setup, the red tissue in the organ bath is the smooth muscle tissues. In this kind of experiment smooth muscle tissue is minimally stretched vertically by two hooks or clips in the organ bath filled with physiological saline solution (PSS). Agonist is added to the PSS to challenge the muscle tissue, muscle contraction is sensed by a force transducer at the top and force is recorded by a computer. Adding antagonist before adding agonist blocks agonist action. PSS may or may not be changed, it depends on your purposes, e.g. if you want to block a type receptors, then you do not want change PSS after you add antagonist to the PSS. Your correct step is that you add antagonist to PSS, wait some time, and add agonist, you keep both antagonist and agonist in the PSS so that you can judge if the receptor blockage by antagonist abolish the agonist action.
The key to this assignment is that you eliminate possible cross-activities of agonists. Cross-activity means an agonist activate more than one types of receptors, you need block each type of the receptor in order to see what type of the receptor is activate to cause contraction. This muscle tissue can have both α and β receptor types and their subtypes, you need to demonstrate convincingly that you only stimulate α1 receptors.
Write an experimental protocol to demonstrate your work, for each step in the protocol you write the chemical(s) you add, why you add, what result you are expecting to see e.g. contract, relax, no response. If the step is to wash the tissue with fresh PSS, then you do not need to indicate the responses.
Here is an example of the answer.
| step | chemical added | response |
| 1. | epinephrine, activate alpha and beta receptors, | blood vessel ring contract slightly. |
| 2. | wash with PSS | |
| 3. | alpha receptor antagonist and norepinerphine, block NE activating alpha receptor. | blood vessel ring should not contract. |
| 4. | wash with PSS | |
| 5. | ⦠| ⦠|
| 6. | ⦠| ⦠|
Discuss your protocol to show the relation between activation of α1 receptors and the vascular smooth muscle contraction.Design the experiemnt and its conclusion/ results.
QUESTION 1
A partial agonist would:
| a) Have lower efficacy than a full agonist | ||
| b) Would be less effective at stabilizing the active form of a receptor than a full agonist | ||
| c) Would have greater intrinsic activity than an antagonist | ||
| d) All of the above |
QUESTION 2
The presence of spare receptors means that a drug would:
| a) Would have its potency unchanged by low levels of noncompetitive antagonists | ||
| b) Still maintain its maximal efficacy at low concentrations of noncompetitive antagonists | ||
| c) Achieve its maximal response without occupying all available receptors | ||
| d) A and C | ||
| e) B and C |
QUESTION 3
A competitive antagonist would:
| a) Increase drug potency | ||
| b) Decrease drug efficacy | ||
| c) Decrease drug potency | ||
| d) Increase drug efficacy |
QUESTION 4
pH trapping explains:
| a) Why drugs will break down when exposed to acidic conditions | ||
| b) Why drugs do not diffuse back and forth between the kidneys and circulation | ||
| c) Why drugs are attracted to adipose tissue | ||
| d) How drugs are metabolized |
QUESTION 5
An ideal drug would have:
| a) High potency, high efficacy, and a large therapeutic index | ||
| b) High potency, high efficacy, and a small therapeutic index | ||
| c) A high ED50, high efficacy, and a large therapeutic index | ||
| d) High intrinsic activity, low affinity, and a low LD50 |
QUESTION 6
Which of the following is most likely to cross the membrane of a cell?
| a) A nonpolar compound | ||
| b) A polar compound | ||
| c) A charged compound | ||
| d) A large compound |
QUESTION 7
Which is not a pharmacodynamic process?
| a) Absorption | ||
| b) Excretion | ||
| c) Metabolism | ||
| d) Digestion |
QUESTION 8
A drug with a low Vd would:
| a) Be less likely to bind to plasma proteins | ||
| b) Have a higher rate of clearance | ||
| c) Disseminate widely through tissues | ||
| d) Remain primarily within the circulation |
QUESTION 9
First-pass metabolism does not occur through which method of drug administration?
| a) Intramuscular | ||
| b) Intravenous | ||
| c) Transdermal | ||
| d) Enteral |
QUESTION 10
A drug with greater efficacy would:
| a) Have a greater maximal response | ||
| b) Require a lower dose to reach its maximal effect | ||
| c) Be less toxic | ||
| d) All of the above |
